The Sears Tower in Chicago, the tallest building in the US, is offering a new way to push your fear of heights to the edge: a glass ledge suspended from its 103rd floor Skydeck. Nicknamed "the ledge", the set of glass balconies opens to the public tomorrow.Tower officials say the inspiration for the balconies came from the hundreds of forehead prints visitors left behind on Skydeck windows every week. The glass is made up of three layers, each 1.3cms thick. The 110-storey skyscraper, which is to be renamed Willis Tower, will also undergo a $350m green renovation.